DE102021111422A1 - Device and method for contactless recording of fingerprints and handprints - Google Patents

Abstract

The invention relates to a device and method for non-contact optical recording of the papillary structure of a hand or parts thereof, which are equivalent to contact-based impressions. The object of the invention is achieved by a device and method for non-contact optical recording of the papillary structure of a hand comprising: - an im a recess (30) in the upper area of the device for fingerprint recording (4), which serves a user for rough orientation of the correct hand positioning (31), - a lighting unit (1) for illuminating the hand or parts thereof (3) with structured light, a camera (2) for capturing light from the lighting unit (1), which is diffusely reflected by the hand or parts thereof (3) in an object plane (21) of the camera (2), wherein- a non-vanishing difference in the distances between the camera and the lighting unit to the Object plane (17) is present to determine a position of the hand or parts thereof (3) with respect to the Sch to determine the focal depth range (9) of the camera (2) by means of a method for determining the structure size in an image recorded by the camera (2), and a computing unit (29) for calculating the position by determining the structure size and for calculating the fingerprint image.

Description

The invention relates to a device and method for contact-free optical recording of the papillary structure of a hand or parts thereof, which are equivalent to contact-based impressions.

Authorities-compliant (contact-based) multi-finger scanners are characterized by the fact that the image field is at least 3.2" x 3.0" (W x H) with a scan of 500 ppi. If one now includes in a contactless recording of a finger that the curved surface of a finger up to a defined tolerance angle 7, as in 2 shown schematically, is to be scanned with 500 ppi, in order to capture the same area as with contact-based scanners, a clear overscan (> 500 ppi in relation to a virtual measurement plane) must take place. The resulting amount of data can usually only be converted into 3D coordinates with a non-negligible amount of time, so that real-time control of the hand position in 3D space is difficult with conventional measurement technology. For the actual measurement task of recording a high-resolution fingerprint, the camera 2 has a specific, narrowly limited depth of field in which the papillary structure of the finger can only be imaged sharply. If the hand or finger is outside the depth of field of the camera 2, a detailed picture is not possible.

Known devices for contactless recording of fingerprints have a wide variety of approaches as to how the hand or finger position can be limited or recorded.
So reveals the U.S. 10,460,145 B2 a device for non-contact optical recording of the characteristics of a hand, two lighting sources and a camera. The hand has to be moved through a vertically restricted free space in order to take the fingerprints.
the U.S. 8,600,123 B2 describes a device for contactless fingerprint recording with a recording volume that is structurally limited in three dimensions and at least one camera for contactless recording of the fingers.

From the KR 2019 0097706 A1 a device for contactless fingerprint recording is known, which requires a distance sensor in addition to the recording camera.
In the DE 10 2019 126 419 A1 the device for contactless fingerprint recording is equipped with a multicolored lighting unit and at least two cameras for 3-dimensional recording of the papillary structure of a hand.
Other devices for optical imaging of the papillary structure of fingers, which have similarly complex additional devices for position detection, are from U.S. 8,971,588 B2 , U.S. 8,953,854 B2 , WO 2018/073335 A1 , CN 104361315B , U.S. 9,734,381 B2 , U.S. 8,224,064 B1 , the U.S. 9,396,382 B2 and U.S. 8,391,590 B2 known.

Furthermore, in the U.S. 10,885,297 B2 a device for the contactless recording of biometric data is described, in which a camera and a light source are directed into an image recording area and a housing guide with a shaft to which a frame held over the electronic unit is attached, which laterally surrounds the recording area and an entry gap for the insertion of the hand having. The shaft to the frame defines the distance between the hand to be measured and the recording camera for the hand or finger image. The disadvantage, however, is that the frame should not be touched by the user, it must leave enough space for hands of different sizes and thus has room for significant deviations from the narrowly limited image recording area of the camera, which means that the depth of field of the camera optics that must be maintained for high-resolution finger recordings is not guaranteed can be.

The invention is based on the object of finding a new possibility for contactless fingerprint recording of a hand or parts thereof, which allows real-time hand distance detection for 3D image data recording of fingerprints without requiring additional distance sensors or auxiliary frames for distance assignment compared to a high-resolution camera.

According to the invention, the object of claims 1 is achieved. Advantageous embodiments are described in the subordinate claims.

The invention is based on the consideration that exact knowledge of the current hand position is required in order to start the 3D recording or processing or in order to communicate correction suggestions for hand positioning to the user of the scanner.
The invention is based on the basic idea of dispensing with additional multi-part distance sensors for contactless fingerprint recordings for hand distance detection (hand position) and for generating highly precise 3D image data from the hand or parts thereof by means of a specially arranged camera-projector combination and structured illumination of the hand . The 3D image data of the upstream distance detection is determined from the camera image, if there is a permissible hand position from a high-resolution The high-precision 3D image data is reconstructed pixel by pixel from the fingerprint image taken and converted into a two-dimensional fingerprint image in a downstream process.
The hand position detection should take place without additional sensors, spatial limitations or complex scanning methods as a distance determination between hand and camera with little computing effort and used as distance information either to offer the user of the device correction suggestions for the position correction of the hand or to focus the camera accordingly or to start the high-precision reconstruction of the 3D image data when the correct position for recording the hand is available.
The device includes an illumination unit for illuminating a spatial area with structured light, in which the depth of field of the camera also lies, the camera being designed to capture light that is diffusely reflected from a hand or parts thereof in the object plane. For this purpose, the lighting unit has a different distance to the depth of field of the camera, since only then is the structural size of the structured illumination on the camera sensor a function of the distance between the hand and the camera, in order to enable quick spatial positioning of the hand or parts of it in relation to to be able to generate on the device for taking fingerprints by determining the structure size.

The invention provides a new possibility for contactless fingerprint recording of a hand or parts thereof, which allows real-time hand distance detection for 3D image data recording of fingerprints without requiring additional distance sensors or auxiliary frames for distance assignment compared to a high-resolution camera.

• 1: ein Prinzipschema der Erfindung zum berührungslosen optischen Aufnehmen der Papillarstruktur einer Hand oder Teilen davon;
• 2: schematisch die Definition eines Toleranzwinkels, der bei der herkömmlichen Fingerabdruckaufnahme auf einer Kontaktfläche entsteht;
• 3: die Bildschärfe im Sinne einer Modulationstransferfunktion (MTF) über der Emissionswellenlänge der Beleuchtungseinheit;
• 4: den Zusammenhang zwischen einer Strukturgröße auf dem Lichtmodulator der Beleuchtungseinheit, die in der Strukturgröße in der Objektebene und entsprechend auf dem Kamerasensor abgebildet wird;
• 5: die Darstellung des Zusammenhanges zwischen Objektabstand und gemessener Strukturgröße der strukturierten Beleuchtung auf dem Sensor der Kamera für ein periodisches Muster des strukturierten Lichts;
• 6: die Darstellung des Zusammenhanges zwischen Objektabstand und gemessener Strukturgröße der strukturierten Beleuchtung auf dem Sensor der Kamera für ein nichtperiodisches Muster des strukturierten Lichts;
• 7: eine bevorzugte Ausführung der Erfindung mit einem Projektor und einer Kamera, deren optische Achsen parallel zueinander ausgerichtet sind und unterschiedliche Abstände zur Objektebene aufweisen;
• 8: eine weitere bevorzugte Ausführung vergleichbar mit 7, bei der Kamera und Beleuchtungseinheit in einer Scheimpflug-Geometrie angeordnet sind;
• 9: eine bevorzugte Ausführung in Modifikation von 8, bei der die Strahlengänge der Kamera und der Beleuchtungseinheit über Umlenkspiegel gefaltet sind;
• 10: eine weitere bevorzugte Ausführung der Erfindung mit einem Projektor als Beleuchtungseinheit und zwei Kameras, wobei der Projektor einen wesentlichen Unterschied im Abstand zur Hand oder Teilen davon im Vergleich zu den beiden Kameras aufweist;
• 11: eine weitere gegenüber 10 modifizierte Ausführung der Erfindung mit zwei Projektoren und drei Kameras, wobei die Projektoren einen wesentlichen Unterschied im Abstand zu Hand oder Teilen davon im Vergleich zu den drei Kameras aufweisen;
• 12: ein Blockdiagramm einer beispielhaften Konfiguration erfindungsgemäßen Verfahrens;
• 13: einen beispielhaften Ablaufplan für das Verfahren zur Positionserkennung der Hand oder Teilen davon;
• 14: einen weiteren beispielhaften Ablaufplan für das Verfahren zur Positionserkennung im Sinne des Abstandes und der Rotation der Hand oder Teilen davon,
• 15: eine schematische Abbildung einer möglichen Ausgestaltungsform der Vorrichtung;
• 16: eine schematische Darstellung korrekter und nicht-korrekter Handpositionierung beispielhaft;
• 17: eine schematische Abbildung einer möglichen Ausgestaltungsform der Vorrichtung inklusive eines als Display ausgestalteten Feedbackmoduls.

The invention is explained in more detail below using exemplary embodiments and illustrations. show:

• 1 : a schematic diagram of the invention for non-contact optical recording of the papillary structure of a hand or parts thereof;
• 2 : Schematic of the definition of a tolerance angle that arises in conventional fingerprint recording on a contact surface;
• 3 : the image sharpness in terms of a modulation transfer function (MTF) versus the emission wavelength of the illumination unit;
• 4 : the relationship between a structure size on the light modulator of the lighting unit, which is imaged in the structure size in the object plane and correspondingly on the camera sensor;
• 5 : the representation of the relationship between the object distance and the measured structure size of the structured illumination on the camera sensor for a periodic pattern of the structured light;
• 6 : the representation of the relationship between the object distance and the measured structure size of the structured illumination on the camera sensor for a non-periodic pattern of the structured light;
• 7 : a preferred embodiment of the invention with a projector and a camera, the optical axes of which are aligned parallel to one another and have different distances from the object plane;
• 8th : Another preferred embodiment comparable to 7 , in which the camera and lighting unit are arranged in a Scheimpflug geometry;
• 9 : a preferred embodiment in modification of 8th , in which the beam paths of the camera and the lighting unit are folded via deflection mirrors;
• 10 : another preferred embodiment of the invention with a projector as the lighting unit and two cameras, the projector having a significant difference in distance to the hand or parts thereof compared to the two cameras;
• 11 : another opposite 10 modified embodiment of the invention with two projectors and three cameras, the projectors having a significant difference in distance to the hand or parts thereof compared to the three cameras;
• 12 1 is a block diagram of an exemplary configuration of the method according to the invention;
• 13 : an exemplary flow chart for the method for position detection of the hand or parts thereof;
• 14 : another exemplary flowchart for the method for position detection in terms of the distance and the rotation of the hand or parts thereof,
• 15 1: a schematic illustration of a possible embodiment of the device;
• 16 : a schematic representation of correct and incorrect hand positioning as an example;
• 17 1: a schematic depiction of a possible embodiment of the device including a feedback module designed as a display.

The invention includes according to the schematic representation of 1 as a basic principle a device for fingerprint recording 4 and for measuring a distance 16 of the camera 2 to an object plane 21, the camera 2 being provided at the same time for the contactless or non-contact optical recording of the papillary structure of at least one finger. The device 4 comprises an illumination unit 1 for illuminating a depth measurement area 24 with structured light and a camera 2 for capturing light that is diffusely reflected by a hand 3 or a part thereof in the object plane 21, with a difference 17 in the distance 15 of Camera 2 and the distance 16 of the lighting unit 1 to the object plane 21 is present, has.
According to the invention, the depth measurement area 24 is described as the area in which the field of view of the lighting unit 13 of the lighting unit 1 and the field of view of the camera 14 overlap in 3D space, as in FIG 1 shown. In the case of the parallel alignment of the optical axis 11 of the lighting unit 1 and the optical axis 12 of the camera 2, there is a lower limit of the depth measurement range 24. In the case of the Scheimpflug geometry (see 8th ) of camera 2 and lighting unit 1, the depth measuring area 24 also has a maximum distance. The depth measurement range 24 corresponds to the depth of field 9 of the camera 2.

The illumination unit 1 contained in the device 4 is described by an optical axis 11, a 2D spatial intensity modulator, a field of view of the illumination unit 13 and a light source. If the lighting unit 1 also includes a lens for imaging the spatial 2D intensity modulator, it is referred to below as a projector 25 . An illumination unit 1 within the meaning of the invention is used to emit structured light, in particular to emit a wavelength (including spectral broadening). It can also be provided that the lighting unit 1 is able to emit two or three wavelengths. An expedient form of the lighting unit 1 can include, for example, one or more LEDs or one or more lasers (not shown).

Another embodiment of the lighting unit 1 emits a broad spectrum of light, such as white light LEDs, light sources based on thermal radiation (incandescent lamp) or gas discharge lamps.

In one embodiment of the invention, the emission spectrum of the lighting unit 1 is in the range from 350 nm to 1000 nm. In a further embodiment of the invention, see FIG. 3 , the emission spectrum is limited to 450 nm to 550 nm to meet FBI MTF requirements.

In a preferred embodiment of the invention, the working distance 26 of the camera 2 is no less than 50 mm and no more than 1500 mm. The lower limit results from a sufficient distance between hand 3 (or parts of it) and camera 2 to avoid touching. The upper limit results from structural reasons.

In a further preferred embodiment variant of the invention, the working distance 26 of the camera 2 is not less than 200 mm and not more than 400 mm.

In a preferred embodiment of the invention, the distance 28 of the lighting unit 1 to the middle depth of field 27 of the camera 2 (or possibly other cameras 2) is no less than 50 mm and no more than 1400 mm. In a further preferred embodiment variant, the distance 28 of the lighting unit 1 to the middle focal depth plane 27 of the (at least one) camera 2 is not less than 130 mm and not more than 400 mm.

The camera 2 of the device 4, described by an optical axis 12 of the camera 2, a sensor and a lens imaging the sensor, has a field of view 14 and a depth of field 9, which is defined by a lower limit 10 of the depth of field 9 and an upper limit 8 of the depth of field 9 is limited. Only in the depth of field 9 can the papillary structures of the hand 3 (or parts thereof) be imaged in high quality and on the sensor of the camera 2 in accordance with the official specifications (FBI guideline, Appendix F: US Department of Justice, Federal Bureau of Investigation, "Electronic Biometry Transmission Specification (EBTS) with Technical and Operational Updates, Version 10.0.9, May 22, 2018).
In an advantageous embodiment within the meaning of the invention, a camera 2 includes an image sensor and a lens. The image sensor within the meaning of the invention is a device that converts an optical signal into an electrical signal that contains the image information. According to the invention, downstream of the image sensor (or the output of the camera 2) can be a computing unit 29, which is used for image information processing. In particular, the computing unit 29 is also used to calculate the spatial information from the image of the image sensor, in particular the 3D detection of a hand 3 or a finger with the papillary structure.
In an advantageous embodiment (according to 8th ) the lighting unit 1 is equipped with a lens and thus forms a projector 25, the projector 25 used as the lighting unit 1 with structured lighting and the camera 2 being fitted in Scheimpflug geometry. This means that the projector 25 and camera 2 in relation to an object plane 21 fulfill an image rectification according to Scheimpflug.
In a further preferred embodiment, as in 9 outlined, is or are the beam paths of the lighting unit 1 and / or the camera 2, folded over one or more deflection mirrors 5 to enable a compact design.

A 2D intensity modulator within the meaning of the invention can comprise a digital light modulator consisting, for example, of one or more DLP chips (Digital Light Processing), one or more LCDs (Liquid Crystal Device) or one or more LCoS ( .Liquid Crystal on Silicon). In addition, according to the invention, analog light modulators such as masks, slides, or scatter and phase modulation discs (for generating speckle patterns) can also be used. In further preferred embodiments of the invention, a lighting unit 1 or a projector 25 and two cameras 2 are used, the lighting unit 1 or the projector 25 being at a different distance from the depth of field 9 compared to the working distance 26 of the camera(s) 2 ( s. 10 ) or two projectors 25 or two lighting units 1 and three cameras 2 are used, with the projectors 25 or the lighting units 1 being at a different distance from the depth of field (9) compared to the working distance 26 of the cameras 2 (see 11 ).
In a preferred embodiment of the invention, the device 4 has a feedback module 35 which makes information about the correct recording, correction suggestions for the hand position or other information accessible to the user via acoustic, haptic or visual signals or combinations thereof.
In a further preferred embodiment of the invention, the feedback module 35 is designed as a display unit 36 in the form of a display or can also be integrated as a row of LEDs in the upper area of the device 4 .

The method according to the invention for real-time determination of the distance of the hand 3 (or parts thereof) from the camera 2 is based on the different distances of the camera(s) 2 and the lighting unit(s) 1 from the hand 3 in the object plane 21 (see 4 ).
The basic idea here is the measurement of the structure size 18 of the structured illumination on the sensor of the camera 2. According to the nomenclature in 4 is projected by the lighting unit 1 a spatially varying structure with the structure size 20 in the object plane 21 (S ₀ ). The structure size 19 on a light modulator of the lighting unit 1 is S _p . The distance 15 of the lighting unit 1 to the object plane 21 (A _p ) describes the distance from a projector 25 used as the lighting unit 1 to the hand 3 (or parts thereof) and A _c describes the distance 16 of the camera 2 to the object plane 21 of the hand 3.
One can show mathematically that the measured structure size 18 of the structured illumination on the camera 2 sensor (Sc) is a non-constant function of the distance 16 (A _c ) from the camera 2 to the object plane 21 whenever a difference 17 (δ ≠ 0) of the distances from camera 2 and lighting unit 1 to object plane 21 is present. $$S_C=f\left(A_c\right)\text{f}\ddot{\text{and}}\text{right}\delta \ne 0$$

This in turn means that for δ ≠ 0 the distance 16 of the camera 2 to the object plane 21 (A _c ) can be determined if the structure size 18 of the structured illumination projected by the lighting unit 1 is taken from the projector 25 onto the sensor of the camera 2 (p _c ) can be measured, which solves the basic problem of distance measurement. $$A_C=f\left(S_c\right)\text{f}\ddot{\text{and}}\text{right}\delta \ne 0$$

In the case of the projection of periodic or quasi-periodic patterns, e.g. one- or two-dimensional sinusoidal patterns or point patterns, the imaged structure size S _c can be easily and efficiently derived from the discrete Fourier transform (DFT) or its fast implementation (FFT) via a local maximum search in the Determine frequency space. This is also possible via a wavelet transformation.
are in 5 the intermediate steps of the method presented are shown for the projection of a sinusoidal pattern onto the hand 3 or parts thereof (fingers of a hand) using a projector 25, which has a different distance 15 to the object plane 21 compared to the camera 2, which is used for the recording . For an almost equal distance to hand 3 (or parts of it) for camera 2 and lighting unit (1), a constant fringe distance or constant spatial frequency (circles) results in the camera image, whereas for the case that the projector 25 only has half the distance has at hand 3, a clear progression of the strip distance with the distance 16 of the camera 2 to the object plane 21 can be recorded.
In 6 the intermediate steps of the method presented here are shown for projected non-periodic patterns (speckles). For an almost identical distance from the object plane 21 for the camera 2 and the lighting unit 1, the camera image produces a constant structure size distribution or constant spatial frequency distribution (circles), whereas in the event that the lighting unit 1 is only half the distance 16 to hand 3 (or parts thereof), there is a clear course of the structure size distribution with the distance 16 of the camera 2 to hand 3 is to be recorded.
If the method described here is applied to a plurality of partial images, a depth map of the recorded and illuminated scene with reduced resolution can be generated, which makes it possible to determine the rotation of the hand 3 .
For the determination of the correct hand positioning 31, a distance of the hand 3 (or parts thereof) and the rotation (twisting), based on the depth of field 9, is determined. For correct hand positioning 31, s. 16 , the parts of the hand 3 to be measured must be planar in the depth of field 9. The image analysis 34 generally describes the method for determining the position and alignment of the hand 3 in relation to the camera 2 from the structure size 18 of the structured illumination from the illumination unit 1, imaged on the sensor of the camera 2, with specific explanations for the method beforehand have been shown as examples, s. 5 and 6 .

• 1 zeigt eine Vorrichtung 4 zum berührungslosen optischen Aufnehmen der Papillarstruktur einer Hand 3 oder Teilen davon, wobei die Vorrichtung 4 eine Beleuchtungseinheit 1 zum Beleuchten einer Hand 3 (oder Teile davon) mit strukturiertem Licht und mindestens eine Kamera 2 zum Erfassen von Licht, das von einer Hand 3 oder eines Teils einer Hand 3 in einer Objektebene 21 diffus reflektiert wird, umfasst, wobei im Wesentlichen eine nichtverschwindende Differenz 17 der Abstände 15, 16 von Beleuchtungseinheit 1 und Kamera 2 zur Objektebene 21 vorhanden ist und die Kamera 2 einen Schärfentiefenbereich 9 besitzt, der durch eine obere Grenze 8 des Schärfentiefenbereichs 9 und eine untere Grenze 10 des Schärfentiefenbereichs 9 beschränkt ist. Eine schnelle Messung der Handposition ist innerhalb des Tiefenmessbereiches 24 möglich, der durch den Überlagerungsbereich aus dem Sichtfeld 14 der Kamera 2 und dem Sichtfeld 13 der Beleuchtungseinheit 1 gegeben ist und der Teile des Schärfentiefenbereichs 9 der Kamera 2 beinhaltet.
• 2 zeigt bildlich die Definition eines Toleranzwinkels 7, welcher bei der herkömmlichen Fingerabdruckaufnahme auf einer Kontaktfläche 6 den Bereich der aufgenommenen Haut beschränkt und der auch bei der kontaktlosen Aufnahme entsprechend den (behördlichen) Anforderungen abgebildet werden muss.
• 3 zeigt die Bildschärfe im Sinne einer Modulationstransferfunktion (MTF) über der Emissionswellenlänge der Beleuchtungseinheit 1. Oberhalb von 640 nm wird das FBI-Kriterium an die Schärfe an keiner Stelle erreicht. Die Bildschärfe wurde berechnet für ein optisch abbildendes System mit einem Arbeitsabstand von 200 mm bei einer Blendenzahl von 2,5.
• 4 zeigt zusätzlich zu den in 1 dargestellten Größen den Zusammenhang auf zwischen einer Strukturgröße 19 auf dem Lichtmodulator der Beleuchtungseinheit 1, die in der Strukturgröße 20 in der Objektebene 21 abgebildet wird. Die Strukturgröße 18 der strukturierten Beleuchtung auf dem Sensor der Kamera 2 ist dabei eine Funktion des Abstands 16 der Kamera 2 zur Objektebene 21, wenn die Differenz 17 der Abstände 15, 16 von Beleuchtungseinheit 1 und Kamera 2 zur Objektebene 21 nicht verschwindend ist.
• 5 zeigt ein Verfahrensbeispiel für die Darstellung des Zusammenhanges zwischen Abstand 16 der Kamera 2 zur Objektebene 21 und gemessener Strukturgröße 18 der strukturierten Beleuchtung auf dem Sensor der Kamera 2 für ein periodisches Muster des strukturierten Lichts der Beleuchtungseinheit 1, was zur Berechnung des Abstandes 16 der Kamera 2 zur realen Objektebene 21 dient, in der die Positionierung der Hand 3 oder Teilen davon erfolgt ist.
• 6 verdeutlicht für ein nichtperiodisches Muster der Beleuchtungseinheit 1 ein weiteres Verfahrensbeispiel für die Darstellung des Zusammenhanges zwischen Abstand 16 der Kamera 2 zur Objektebene 21 und gemessener Strukturgröße 18 der strukturierten Beleuchtung auf dem Sensor der Kamera 2.
• 7 zeigt eine bevorzugte Ausführung der Vorrichtung 4 zum berührungslosen optischen Aufnehmen der Papillarstruktur einer Hand 3 oder Teilen davon, wobei die Vorrichtung 4 einen Projektor 25 zum Beleuchten der Hand mit strukturiertem Licht sowie eine Kamera 2 zum Erfassen von Licht, das von der Hand 3 oder eines Teils davon diffus reflektiert wird, umfasst, wobei ein Projektor 25 als Beleuchtungseinheit 1 im Wesentlichen eine nichtverschwindende Differenz 17 der Abstände 15, 16 von Beleuchtungseinheit 1 und Kamera 2 zur Objektebene 21 aufweist, um die in 5 und 6 beschriebenen Verfahren zur Positionsbestimmung der Hand 3 (oder Teilen davon) anwenden zu können.
• 8 zeigt eine bevorzugte Ausführung vergleichbar mit 7, jedoch mit dem Unterschied, dass Kamera 2 und Beleuchtungseinheit 1 in einer Scheimpflug-Geometrie angeordnet sind. Dadurch ergeben sich die Vorteile, dass einerseits im Kamerabild keine durch die Beleuchtungseinheit 1 nicht ausgeleuchteten Bereiche auftreten können und andererseits der Schärfentiefenbereich 9 von Kamera 2 und Beleuchtungseinheit 1 parallel überlappend ausgerichtet sein können.
• 9 zeigt eine bevorzugte Ausführung aufbauend auf 8 mit dem Unterschied, dass die Strahlengänge der Kamera 2 und der Beleuchtungseinheit 1 über Umlenkspiegel 5 gefaltet sind, um eine kompaktere, raumsparende Bauweise der Vorrichtung 4 zu erreichen.
• 10 zeigt eine bevorzugte Ausführung der Vorrichtung 4 zum berührungslosen optischen Aufnehmen der Papillarstruktur einer Hand 3 oder Teilen davon, wobei die Vorrichtung 4 einen Projektor 25 zum Beleuchten der Hand 3 mit strukturiertem Licht und zwei Kameras 2 zum Erfassen von Licht, das von einer Hand 3 oder eines Teils davon diffus reflektiert wird, umfasst, wobei im Wesentlichen eine nichtverschwindende Differenz 17 der Abstände 15, 16 von Beleuchtungseinheit 1 und Kamera(s) 2 zur Objektebene 21 vorhanden ist. Durch diese Konfiguration einer zusätzlichen Kamera 2 ist es möglich, das räumliche Sichtfeld im Sinne eines höheren Toleranzwinkels 7 zu erweitern.
• 11 zeigt eine bevorzugte Ausführung der Vorrichtung 4 zum berührungslosen optischen Aufnehmen der Papillarstruktur einer Hand 3 oder Teilen davon, wobei die Vorrichtung 4 zwei Projektoren 25 zum Beleuchten der Hand 3 mit strukturiertem Licht sowie drei Kameras 2 zum Erfassen von Licht, das von einer Hand 3 oder eines Teils davon diffus reflektiert wird, umfasst, wobei im Wesentlichen eine nichtverschwindende Differenz 17 der Abstände 15, 16 von Beleuchtungseinheit(en) 1 und Kamera(s) 2 zur Objektebene 21 vorhanden ist.
• 12 zeigt ein Blockdiagramm einer beispielhaften Konfiguration, wobei die Datenaufnahme von der Recheneinheit 29 angefordert wird, was ein Trigger-Signal auf einem Datenbus auslöst, welcher in der Vorrichtung 4 dazu führt, dass ein Projektor 25 als spezielle Ausführung der Beleuchtungseinheit 1 ein Streifenmuster projiziert und synchron von einer Kamera 2 ein Bild von der zu messenden Hand 3 mit dem projizierten Streifenmuster aufgenommen wird. Das Bild wird über einen weiteren Datenbus an die Datenverarbeitung der Recheneinheit 29 weitergeleitet wird, in der die Höhenbestimmung und Rotationsbestimmung der Handpositionierung durchgeführt werden, auf Basis von deren Ergebnissen eine Korrekturbestimmung erfolgt, welche über einen weiteren Datenbus dem Nutzer ein Feedback auf einer Anzeigeeinheit 36 zur Verfügung stellt.
• 13 zeigt einen beispielhaften Ablaufplan für das Verfahren zur Positionserkennung, bei dem nach dem Starten des Verfahrens die Ansteuerung der Kamera 2 zu dem Erhalt von Bilddaten führt, wonach der Schritt Bilddaten versenden an Recheneinheit 29 eine Datenverarbeitung zur Erkennung der Handposition erfolgt, wobei bei unkorrekte Handpositionierung im Sinne fehlerhafter Abstände 32 eine Korrektur der Position angefordert wird und dies über die Anzeigeeinheit 36 dem Nutzer signalisiert wird. Danach startet eine weitere Aufnahme; bei akzeptabler Handposition ist das Verfahren zur exakten Positionsbestimmung beendet und eine akzeptable Positionierung der Hand 3 im Schärfentiefenbereich 9 gewährleistet die fehlerfreie und hochauflösende Bildaufnahme der Papillarstruktur einer Hand 3 oder einzelnen Fingern davon.
• 14 zeigt einen beispielhaften Ablaufplan für das Verfahren zur Positionserkennung, bei dem nach dem Starten des Verfahrens die Ansteuerung der Kamera 2 zu dem Erhalt von Bilddaten führt, wonach der Schritt Bilddaten versenden an Recheneinheit 29 eine Datenverarbeitung zur Erkennung der Handposition erfolgt, wobei bei unkorrekte Handpositionierung im Sinne fehlerhafter Abstände 32 eine Korrektur der Position angefordert wird und dies über die Anzeigeeinheit 36 dem Nutzer signalisiert wird. Anschließend startet eine weitere Aufnahme, bei akzeptabler Handposition wird die Rotation der Hand analysiert, wobei bei unkorrekte Handpositionierung im Sinne fehlerhafter Rotation 33 eine Korrektur der Rotation angefordert wird und dies über die Anzeigeeinheit 36 dem Nutzer signalisiert wird. Danach startet eine weitere Aufnahme; bei akzeptabler Handrotation ist das Verfahren zur exakten Positionsbestimmung beendet und eine akzeptable Positionierung der Hand in der Schärfentiefenbereich 9 gewährleistet die fehlerfreie und hochauflösende Bildaufnahme der Papillarstruktur einer Hand 3 oder Teilen davon.
• 15 zeigt beispielhaft die Ausgestaltung der Vorrichtung zur Fingerabdruckaufnahme 4 mit einer an der Oberseite angebrachten Aussparung 30 für die korrekte Handpositionierung 31, die dem Nutzer zugewandt ist.
• 16 zeigt die korrekte Handpositionierung 31, bei der die Hand oder Teile derer korrekt zwischen oberer Grenze 8 des Schärfentiefenbereichs 9 und untere Grenze 10 des Schärfentiefenbereichs 9 liegen. Außerdem wird eine unkorrekte Handpositionierung im Sinne fehlerhafter Abstände 32 der Hand oder Teile derer dargestellt. Außerdem wird eine unkorrekte Handpositionierung im Sinne fehlerhafter Rotation 33 der Hand 3 dargestellt.
• 17 zeigt beispielhaft die Ausgestaltung der der Vorrichtung zur Fingerabdruckaufnahme 4 mit einer an der Oberseite angebrachten Aussparung 30 für die korrekte Handpositionierung 31, die dem Nutzer zugewandt ist inklusive eines Feedbackmoduls 35, welches als Anzeigeeinheit 36 (Display) ausgestaltet ist.

In a preferred embodiment of the invention, data acquisition is requested by a computing unit 29, which triggers a trigger signal on a data bus. In the device 4 this results in at least one lighting unit 1 projecting a stripe pattern and synchronously recording an image of the hand 3 or parts thereof with the projected stripe pattern by at least one camera 2 . This is forwarded via a further data bus to the data processing unit of the arithmetic unit 29, in which the distance is determined by searching for a maximum in the frequency space of the entire image and the determination of the rotation is carried out by analyzing the maximums in the frequency space of raster elements of the image. A correction is determined on the basis of the analysis results, which is made available to the user as feedback on a display unit 36 via a further data bus. Another recording then starts, with an acceptable positioning of the hand 3 in the depth measurement area 24, which is communicated to the user via the display unit 36, either with a new data recording via the camera 2 or with the data processing to a 3D image or to a fingerprint image will.

• 1 shows a device 4 for non-contact optical recording of the papillary structure of a hand 3 or parts thereof, the device 4 having a lighting unit 1 for illuminating a hand 3 (or parts thereof) with structured light and at least one camera 2 for detecting light emitted by a Hand 3 or a part of a hand 3 is diffusely reflected in an object plane 21, with essentially a non-vanishing difference 17 of the distances 15, 16 of the illumination unit 1 and camera 2 to the object plane 21 being present and the camera 2 having a depth of field 9, which is limited by an upper limit 8 of the depth of field 9 and a lower limit 10 of the depth of field 9 . A quick measurement of the hand position is possible within the depth measurement range 24 , which is given by the overlapping range from the field of view 14 of the camera 2 and the field of view 13 of the lighting unit 1 and which includes parts of the depth of field 9 of the camera 2 .
• 2 shows the definition of a tolerance angle 7, which in conventional fingerprint recording on a contact surface 6 limits the area of the recorded skin and which must also be mapped in contactless recording in accordance with the (official) requirements.
• 3 shows the image sharpness in terms of a modulation transfer function (MTF) over the emission wavelength of the illumination unit 1. Above 640 nm, the FBI criterion for sharpness is not achieved at any point. The sharpness of the image was calculated for an optical imaging system with a working distance of 200 mm and an f-number of 2.5.
• 4 shows in addition to the in 1 sizes shown on the relationship between a structure size 19 on the light modulator of the lighting unit 1, which is imaged in the structure size 20 in the object plane 21. The structure size 18 of the structured illumination on the sensor of the camera 2 is a function of the distance 16 of the camera 2 to the object plane 21 if the difference 17 of the distances 15, 16 of the illumination unit 1 and camera 2 to the object plane 21 is not negligible.
• 5 shows a method example for the representation of the relationship between the distance 16 of the camera 2 to the object plane 21 and the measured structure size 18 of the structured illumination on the sensor of the camera 2 for a periodic pattern of the structured light of the illumination unit 1, which is used to calculate the distance 16 of the camera 2 serves for the real object plane 21, in which the positioning of the hand 3 or parts thereof has taken place.
• 6 1 illustrates another pattern for a non-periodic pattern of the lighting unit 1 Process example for the representation of the relationship between the distance 16 of the camera 2 to the object plane 21 and the measured structure size 18 of the structured illumination on the sensor of the camera 2.
• 7 shows a preferred embodiment of the device 4 for non-contact optical recording of the papillary structure of a hand 3 or parts thereof, the device 4 having a projector 25 for illuminating the hand with structured light and a camera 2 for detecting light from the hand 3 or a part of which is diffusely reflected, with a projector 25 as the lighting unit 1 essentially having a non-vanishing difference 17 in the distances 15, 16 from the lighting unit 1 and the camera 2 to the object plane 21, in order to 5 and 6 to be able to apply the method described for determining the position of the hand 3 (or parts thereof).
• 8th shows a preferred embodiment comparable to 7 , but with the difference that camera 2 and lighting unit 1 are arranged in a Scheimpflug geometry. This results in the advantages that on the one hand no areas not illuminated by the illumination unit 1 can appear in the camera image and on the other hand the depth of field 9 of the camera 2 and the illumination unit 1 can be aligned parallel to overlap.
• 9 shows a preferred embodiment based on 8th with the difference that the beam paths of the camera 2 and the lighting unit 1 are folded via deflection mirrors 5 in order to achieve a more compact, space-saving design of the device 4.
• 10 shows a preferred embodiment of the device 4 for non-contact optical recording of the papillary structure of a hand 3 or parts thereof, the device 4 having a projector 25 for illuminating the hand 3 with structured light and two cameras 2 for detecting light from a hand 3 or part of it is diffusely reflected, with essentially a non-vanishing difference 17 of the distances 15, 16 from the lighting unit 1 and the camera(s) 2 to the object plane 21 being present. This configuration of an additional camera 2 makes it possible to expand the spatial field of view in terms of a higher tolerance angle 7 .
• 11 shows a preferred embodiment of the device 4 for non-contact optical recording of the papillary structure of a hand 3 or parts thereof, the device 4 having two projectors 25 for illuminating the hand 3 with structured light and three cameras 2 for detecting light from a hand 3 or part of it is diffusely reflected, wherein essentially a non-vanishing difference 17 of the distances 15, 16 from the lighting unit(s) 1 and camera(s) 2 to the object plane 21 is present.
• 12 shows a block diagram of an exemplary configuration, the data acquisition being requested by the arithmetic unit 29, which triggers a trigger signal on a data bus, which in the device 4 causes a projector 25 as a special version of the lighting unit 1 to project a stripe pattern and synchronously an image of the hand 3 to be measured with the projected stripe pattern is recorded by a camera 2 . The image is forwarded via a further data bus to the data processing unit of the arithmetic unit 29, in which the determination of the height and rotation of the hand positioning are carried out, on the basis of the results of which a correction is determined, which provides the user with feedback on a display unit 36 via a further data bus provides.
• 13 shows an exemplary flow chart for the method for position detection, in which, after starting the method, the activation of camera 2 leads to the receipt of image data, after which the step of sending image data to processing unit 29 involves data processing to identify the hand position, with incorrect hand positioning in the In the sense of incorrect distances 32, a correction of the position is requested and this is signaled to the user via the display unit 36. Then another recording starts; if the hand position is acceptable, the method for determining the exact position is ended and an acceptable positioning of the hand 3 in the depth of field 9 ensures error-free and high-resolution imaging of the papillary structure of a hand 3 or individual fingers thereof.
• 14 shows an exemplary flow chart for the method for position detection, in which, after starting the method, the activation of camera 2 leads to the receipt of image data, after which the step of sending image data to processing unit 29 involves data processing to identify the hand position, with incorrect hand positioning in the In the sense of incorrect distances 32, a correction of the position is requested and this is signaled to the user via the display unit 36. Then another recording starts, if the hand position is acceptable, the rotation of the hand is analyzed, and if the hand is incorrect positioning in terms of incorrect rotation 33 a correction of the rotation is requested and this is signaled to the user via the display unit 36 . Then another recording starts; If the hand rotation is acceptable, the method for determining the exact position is ended and an acceptable positioning of the hand in the depth of field 9 ensures error-free and high-resolution imaging of the papillary structure of a hand 3 or parts thereof.
• 15 shows an example of the configuration of the device for taking fingerprints 4 with a recess 30 attached to the upper side for the correct positioning of the hand 31, which faces the user.
• 16 shows the correct hand positioning 31, in which the hand or parts of it lie correctly between the upper limit 8 of the depth of field 9 and the lower limit 10 of the depth of field 9. In addition, incorrect hand positioning in the sense of incorrect distances 32 of the hand or parts thereof is shown. In addition, an incorrect hand positioning in the sense of incorrect rotation 33 of the hand 3 is shown.
• 17 shows an example of the configuration of the device for fingerprint recording 4 with a recess 30 attached to the top for correct hand positioning 31, which faces the user, including a feedback module 35, which is configured as a display unit 36 (display).

Reference List

1

lighting unit

2

camera

3

hand (or parts thereof)

4

Device for fingerprint recording

5

deflection mirror

6

contact surface

7

tolerance angle

8th

upper limit of the depth of field

9

depth of field

10

lower limit of the depth of field

11

optical axis of the lighting unit

12

optical axis of the camera

13

Field of view of the lighting unit

14

field of view of the camera

15

Distance of the lighting unit to the object plane

16

Distance of the camera to the object plane

17

Difference in the distances from the camera and lighting unit to the object plane

18

Structure size of the structured illumination on the camera sensor

19

Structure size on the projector's light modulator

20

Structure size of the structured illumination in the object plane

21

object level

22

effective focal length of the camera lens

23

effective focal length of the lighting unit

24

depth measurement range

25

projector

26

working distance of the camera

27

medium depth of field

28

Distance of the illumination unit to the mean depth of field

29

unit of account

30

recess

31

correct hand positioning

32

incorrect hand positioning in terms of incorrect spacing

33

incorrect hand positioning in terms of incorrect rotation

34

Image Analysis

35

feedback module

36

display unit

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

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• DE 102019126419 A1 [0004]
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• US8953854B2 [0004]
• WO 2018/073335 A1 [0004]
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Claims (16)

Device for non-contact optical recording of the papillary structure of a hand (3) or parts thereof, comprising: - a recess (30) in the upper area of the device for recording fingerprints (4), which is used by a user for rough orientation of the correct hand positioning (31), - an illumination unit (1) for illuminating the hand or parts thereof (3) with structured light, a camera (2) for capturing light from the illumination unit (1) emitted by the hand or parts thereof (3) in an object plane (21 ) of the camera (2) is diffusely reflected, where - there is a non-vanishing difference in the distances from the camera and the lighting unit to the object plane (17) in order to determine a position of the hand or parts thereof (3) in relation to the depth of field (9) of the camera (2) by means of a method for determining the structure size in one of to determine the image captured by the camera (2), and - A computing unit (29) for calculating the position by means of determining the structure size and for calculating the fingerprint image. device after claim 1 , the working distance of the camera (26) being at least 50 mm and at most 1500 mm. Device according to one of Claims 1 until 2 , wherein the distance (28) of the lighting unit (1) to the focal range (9) of the camera (2) is at least 50 mm and at most 1400 mm. device after claim 1 , wherein optical paths of the lighting unit (1) and the camera (2) along the optical axis (12) of the camera (2) and the optical axis (11) of the lighting unit (1) are non-parallel. device after claim 4 , wherein the beam paths of the lighting unit (1) and the camera (2) are folded to save space via deflection mirrors. Device according to one of Claims 1 until 5 , wherein the lighting unit (1) has an emitted light spectrum which is in the range from 350 nm to 1000 nm. Device according to one of Claims 1 until 6 , wherein the lighting unit (1) has a 2D intensity modulator with an upstream lens and with a DLP, LCD or LCoS system. Device according to one of Claims 1 until 6 , wherein the 2D intensity modulator of the lighting unit (1) has a 2D intensity modulator with a diffractive element. Device according to one of Claims 1 until 8th , wherein the lighting unit (1) has a 2D intensity modulator with an upstream lens and with a rigid, rotating or translationally displaceable transmitted light image. Device according to one of Claims 1 until 9 , In addition, there is a feedback module (35) for outputting acoustic, haptic or visual signals or combinations thereof, with which a user receives information about the recording of the papillary structure from the hand with correct hand positioning (31) or correction suggestions for eliminating incorrect hand positioning in the sense faulty distances (32) or incorrect hand positioning in terms of faulty rotation (33) or other information can be made accessible. device after claim 10 , wherein the feedback module (35) for generating visual signals is a display unit (36) integrated in the device for fingerprint recording (4). device after claim 10 , wherein the feedback module (35) for generating visual signals is an LED line integrated in the upper area of the device. Method for non-contact optical recording of the papillary structure of a hand or parts thereof (3), in which the hand of a user is positioned in a depth measurement area (24) of the device for fingerprint recording (4), the user passing this through a recess (30) of the device target position is specified, containing the steps: - illuminating the hand or parts of it (3) with structured light from a lighting unit (1), with a difference in the distances between the camera and lighting unit and the object plane (17) being present, - detecting structured light of the Lighting unit (1), which is diffusely reflected by the hand or parts thereof (3), with the camera (2) as an image of an illumination pattern and transmitting the recorded image to a computing unit (29), - determining the structure size of the structured illumination on the Sensor of the camera (18) in the computing unit (29), - calculating the position of the hand or parts thereof (3) in the computing unit it (29) by means of image analysis (34) from structure size of the structured illumination on the sensor of the camera (18) with regard to known structure size on the light modulator (19), - calculating fingerprint images of the hand or parts thereof (3) if their position is entirely within the depth of field (9). procedure after Claim 13 , where - the structure size of the structured illumination is determined on the sensor of the camera (18) by means of image analysis (34) in the frequency domain. procedure after Claim 13 , wherein - the correct hand positioning (31) is determined by means of image analysis (34) in terms of incorrect distances or incorrect rotation of the hand (3) with respect to the camera (2). procedure after Claim 13 , wherein - in the case of incorrect hand positioning in terms of faulty distances (32) or incorrect hand positioning in terms of faulty rotation (33), correction instructions are output via a feedback module (35).

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